Helicopters are traditionally powered by one or more gas turbines, wherein the high speed of the gas turbine must be reduced by a gearbox, which mechanically drives the rotors of the helicopter, for example a main rotor or tail rotor. Such a gearbox obviously places high demands on reliability, and is thus correspondingly complicated, heavy and expensive.
Known from DE 10 2006 056 354 A1 is a hybrid drive for aircraft that comprises a gas turbine for generating a first driving energy and an electric motor for generating a second driving energy. The gas turbine and electric motor are designed in such a way that the first and/or second driving energy can be made available to a drive unit, for example a propeller, of the aircraft. Required for this purpose is a coupling between the gas turbine and electric motor, or a first coupling between the gas turbine and propeller shaft, and a second coupling between the electric motor and propeller shaft. A fuel cell system and a battery can be provided for the electric motor.
Known from DE 10 2006 056 356 A1 is a drive with several energy converters for an aircraft, wherein each of the energy converters can be designed as a gas turbine, reciprocating piston engine or electric motor. Required here as well is a clutch between a first and second energy converter, or between the first and second energy converter and a propeller. Let it also be mentioned in this conjunction that only one electric motor is used for cruising flight or in proximity to an airport, while an internal combustion engine is additionally required during takeoff and landing.
WO 2008/086774 A2 proposes an aircraft propeller drive with a propeller, a motor and a drive train between the propeller and motor, wherein the drive train comprises a torsional vibration damper. Between a diesel engine and gearbox input shaft an electric machine may be provided, which can charge a battery when connected as a generator, and can additionally power the diesel engine when connected as an electric motor and supplied by the battery.